03145: pacman, pacmanm: Joystick input when changing direction seems different to original board

ID	Category [?]	Severity [?]	Reproducibility	Date Submitted	Last Update
03145	DIP/Input	Minor	Always	May 6, 2009, 22:02	May 6, 2009, 23:50

Tester	mojo	View Status	Public	Platform	MAME (Official Binary)
Assigned To		Resolution	Open	OS	Windows XP/Vista 64-bit
Status [?]	Acknowledged			Driver	pacman/jrpacman.cpp
Version	0.130u4	Fixed in Version		Build	Normal
		Fixed in Git Commit		Github Pull Request #

Summary	03145: pacman, pacmanm: Joystick input when changing direction seems different to original board
Description	I have an original Midway PacMan board, which I have tried with both Midway and Namco ROMs and compared it with MAME. Using the same joystick on both MAME and the original board, the original seems a lot less prone to the player getting "stuck" when going round a corner. By "stuck" I mean Pacman does not corner smoothly, but either sticks for a moment before then changing direction or misses a turn entirely. I have experimented with different joysticks, because at first I thought it might be because I was using an 8 way joystick, but even with a 4 way restrictor plate the original game is less prone to this than MAME. I checked the schematics but can't see any obvious reason why there would be any difference, but several friends have come to the same conclusion on the same and different PCs. I myself have checked three different PCs side by side with the original. My only guess is that it is to do with when the joystick is being read by MAME. Presumably the inputs are just port/memory mapped for the Z80 so it reads the status the instant the code is executed, while MAME presumably polls Windows for updates some how. As I build my own USB joystick interfaces I tried setting the minimum 10ms update intervals for low speed HID devices, but it didn't help.
Steps To Reproduce	Play game normally.
Additional Information
Github Commit

Flags	Verified with Original
Regression Version
Affected Sets / Systems	pacman, pacmanm

Attached Files